Mucinous metaplasia of apocrine duct.

Mucinous syringometaplasia is a rare condition characterized by the presence of mucinous cells lining eccrine ducts. Because most occurrences are on the palms and soles, the disorder is generally considered to be the result of chronic trauma or pressure. We describe an example of mucinous metaplasia involving an apocrine duct on the left arm of a 57-year-old woman. Histopathologic study demonstrated that in deeper areas of the invagination, the lining of the lumen consisted of columnar cells showing decapitation secretion and that the invagination was connected to a rudimentary hair follicle. These histopathologic features support the possibility that the involved duct was an apocrine one. We discuss the differential diagnosis with those cutaneous adnexal neoplasms in which the presence of mucinous cells has been described.